mavsdk_tests: remove opt_flow test
mavsdk_tests: remove opt_flow test

It doesn't actually seem to work.

acfloria/Firmware,krbeverx/Firmware,PX4/Firmware,krbeverx/Firmware,acfloria/Firmware,PX4/Firmware,PX4/Firmware,acfloria/Firmware,krbeverx/Firmware,acfloria/Firmware,PX4/Firmware,krbeverx/Firmware,acfloria/Firmware,krbeverx/Firmware,acfloria/Firmware,PX4/Firmware,acfloria/Firmware,krbeverx/Firmware,krbeverx/Firmware,PX4/Firmware,PX4/Firmware